NMR-Spektren von Verdazylen

Neugebauer, Franz A.; Trischmann, Heinrich; Taigel, Gisela

doi:10.1007/bf00901375

Cited by 14 publications

(3 citation statements)

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“…More recently the formation of reactive primary bromide Ih and its reaction with pyridine to form the corresponding pyridinium salt was reported . It should be mentioned that verdazyls with the carbethoxy, nitro and 4-methoxycarbonylphenyl substituents in the C(3) position were reported, but their transformations were not investigated.…”

Section: Introductionmentioning

confidence: 99%

Functional Group Transformations in Derivatives of 6-Oxoverdazyl

et al. 2013

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Transformations of functional groups, such as OCH2Ph, OCOPh, NO2 and I, in 1,3,5-triphenyl-6-oxoverdazyls 1a-1e were investigated in order to expand the range of synthetic tools for incorporation of the verdazyl system into more complex molecular architectures and to increase spin delocalization. Thus, Pd-catalyzed debenzylation of the OCH2Ph group or basic hydrolysis of the OCOPh group gave the phenol functionality, which was acylated, but could not be alkylated. Orthogonal deprotection of diphenol functionality was also demonstrated in radical 1c. Pt-catalyzed reduction of the NO2 group led to the aniline derivative, which was acylated. Attempted C-C coupling reactions to iodophenyl derivatives 1e and 5e were unsuccessful. Selected verdazyl radicals were characterized by EPR and electronic absorption spectroscopy, and results were analyzed with the aid of DFT computational methods.

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Section: Introductionmentioning

confidence: 99%

Functional Group Transformations in Derivatives of 6-Oxoverdazyl

et al. 2013

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“…The N-alkylated formazan 10 can occasionally be isolated, and then heated to proceed to the leuco verdazyl and, ultimately (in the presence of an oxidant), the verdazyl. 12,14,15 A variation on the formazan synthesis involves their reactions with forma1dehyde or aliphatic aldehydes under basic conditions (Scheme 7.2). This reaction presumably also proceeds via a leuco intermediate, based on the observation that oxygen is required for radical formation.…”

Section: Verdazyls From Formazansmentioning

confidence: 99%

“…EPR data for verdazyls with electron donating or electron withdrawing aromatic substituents on the nitrogen atoms show predictable changes in the hyperfine couplings: more electron poor groups (e.g., nitrophenyl) have relatively smaller hyperfine couplings to the N1/N5 pair as the electron withdrawing groups compete for the nitrogen's lone pair. 12,15,20 The EPR spectra of 6-oxoverdazyls 7 and 6-thioxoverdazyls 8 differ in subtle but systematic ways from those of the Kuhn verdazyls 6. For 7 and 8 the N1/N5 constants are consistently smaller than N2/N4; typical values for N1/N5 are 5.1-5.4 G if R /R = alkyl and ∼4.5 G if the R /R = aryl; the N2/N4 constants are consistently 6.3-6.6 G. 42,47 The differences between these and the Kuhn radicals can be understood in the context of the resonance structures of Figure 7.3 as applied to the 6-oxoverdazyl framework: the electron withdrawing carbonyl group adjacent to N1/N5 competes for electron density from these atoms, thereby decreasing the relative importance of resonance structures c and d (compared to a and b).…”

Section: Verdazyls From Hydrazides and Bis-hydrazides: 6-oxoverdazylsmentioning

confidence: 99%